This research aims to develop improved maxillofacial prosthetic materials based on a unique methacrylic siloxane polymer. In Phase I, the formulations of the maxillofacial prosthetic materials were studied as functions of cure temperature, initiator concentration, filler concentration, and the nature and the concentration of the crosslinkers. The materials were evaluated in terms of hardness, ultimate elongation, tensile strength, tear strength and bonding strength to adhesives. The dispersibility of pigments with the maxillofacial materials was studied. Color stability of the materials with and without pigments and uv stabilizers was investigated. In Phase II research, the performance of the maxillofacial materials will be improved by further optimizing the material formulations. The optimization will be achieved by: 1. Broadening the selection of the crosslinking agents, 2. Determination of the mechanical properties, hardness, ultimate elongation, tensile strength, tear strength and adhesive bonding strength, 3. Optimization of the maxillofacial material formulations including the determination of optimum cure temperature and time, 4. Development of both intrinsic and extrinsic coloration processes, 5. Evaluating and improving the color stability, 6. Transfer of material technology to the University of Minnesota School of Dentistry for fabrication of clinical prostheses, and 7. Fabrication, application, and evaluation of the clinical prostheses. PROPOSED COMMERCIAL APPLICATION: Development of high performance maxillofacial prosthetic materials which cure at low temperatures (less than 100 degrees Celcius), have high tear strength, strong bonding to adhesives, are capable of accepting and retaining intrinsic and extrinsic coloration, have improved color stability, and are suitable for clinical applications.